Method and apparatus for restoring multi level/phase modulation data

Abstract

A method and apparatus for receiving multi level/phase modulation data and restoring the received data to its original data state. The received data is demodulated and deinterleaved. The deinterleaved data is decoded in a Trellis decoder. Here, when the data to be deinterleaved is not synchronized, the deinterleaving sync is shifted, the deinterleaving operation is again repeated, thereby correcting ±180° phase error. The multi level/phase decoder includes an axis exchanger for exchanging the I-axis data and the Q-axis with each other. Accordingly, when the sync is not matched even though the sync is shifted by one cycle in the deinterleaver, the axis exchange is performed in the axis exchanger. Then, the axis-exchanges data is deinterleaved and Trellis-decoded, to thereby correct ±90° phase error.

What is claimed is: 
     
       1. A method for receiving multi level/phase modulation data and restoring the multi level/phase modulation data into original data, said method comprising the steps of: receiving I-axis data and Q-axis data which is obtained by demodulating the received multi level/phase modulation data;   deinterleaving the I-axis data and the Q-axis data;   Viterbi-decoding the deinterleaved data and determining if the Viterbi-decoded data is synchronized;   shifting by a predetermined interval the data deinterleaving sync position during said deinterleaving step when the Viterbi-decoded data is not synchronized; and   exchanging the I-axis data and the Q-axis data with each other when it is determined that the Viterbi-decoded data is not synchronized for a predetermined number of times.   
     
     
       2. A method for restoring multi level/phase modulation data according to claim 1, wherein said step of exchanging the I-axis data and the Q-axis data with each other comprises the steps: generating a predetermined out-of-sync signal if a sync condition is not detected by the result of Veterbi decoding;   counting the out-of-sync signals;   generating a control signal when the counted result is equal to the number of times the deinterleaving sync position is shifted for one cycle; and   exchanging the axes of the I-axis data and Q-axis data with each other in response to generation of the control signal.   
     
     
       3. A method for restoring multi level/phase modulation data according to claim 2, wherein said step of exchanging the axes comprises the steps of: selecting the I-axis data according to the control signal to supply the selected I-axis data so as to be supplied to the Q-axis transmission channel; and   selecting the Q-axis data according to the control signal to supply the selected Q-axis data so as to be supplied to the I-axis transmission channel.   
     
     
       4. A method for restoring multi level/phase modulation data according to claim 3, wherein said step of switching the I-axis to the Q-axis comprises the step of inverting the I-axis data and converting the inverted data into the Q-axis data. 
     
     
       5. An apparatus for receiving multi level/phase modulation data and restoring the multi level/phase modulation data into original data, said apparatus comprising: input ports for receiving I-axis data and Q-axis data which is obtained by demodulating the received multi level/phase modulation data, respectively;   an axis exchanger portion connected to said input ports for receiving the I-axis data, the Q-axis data and a predetermined control signal and selectively exchanging the axes of the I-axis data and the Q-axis data according to said control signal;   deinterleaver means for deinterleaving the I-axis data and the Q-axis data which is outputted from the axis exchanger, respectively;   a Viterbi-decoding portion for decoding the deinterleaved data according to a Viterbi algorithm and outputting a predetermined out-of-sync signal when it is determined that the Viterbi-decoded data is synchronized as a result; and   a sync detecting portion for detecting the out-of-sync signal outputted from the Viterbi-decoding portion to supply a sync adjustment control signal for shifting a data deinterleaving sync position to the deinterleaver and to supply said control signal for controlling axis exchange to the axis exchanger.   
     
     
       6. An apparatus for receiving multi level/phase modulation data according to claim 5, wherein said deinterleaver means comprises a first deinterleaver for deinterleaving the input data and outputting the deinterleaved data as the I-axis data; and a second deinterleaver for deinterleaving the input data and outputting the deinterleaved data as the Q-axis data.   
     
     
       7. An apparatus for receiving multi level/phase modulation data according to claim 5, wherein said axis exchanger portion comprises: a first switch of which the input port is connected to an I-axis data input terminal, a first output terminal is an input port of said first deinterleaver, and a second output terminal is connected to an input port of said second deinterleaver via an inverter; and   a second switch SW2 of which the input port is connected to an Q-axis data input terminal, a first output terminal is the other input port of said second deinterleaver, and a second output terminal is connected to the other input port of said first deinterleaver.   
     
     
       8. An apparatus for receiving multi level/phase modulation data according to claim 6, wherein said axis exchanger portion comprises: a first switch of which the input port is connected to an I-axis data input terminal, a first output terminal is an input port of said first deinterleaver, and a second output terminal is connected to an input port of said second deinterleaver via an inverter; and   a second switch SW2 of which the input port is connected to an Q-axis data input terminal, a first output terminal is the other input port of said second deinterleaver, and a second output terminal is connected to the other input port of said first deinterleaver.   
     
     
       9. An apparatus for receiving multi level/phase modulation data according to claim 5, wherein said sync detector comprises: a counter for receiving an out-of-sync signal supplied from said Viterbi decoder as clock and performing a counting; and   means for generating said control signal for said axis exchanger when the counted result of said counter reaches a value of a predetermined modulo-N.   
     
     
       10. An apparatus for receiving multi level/phase modulation data according to claim 8, wherein said modulo-N value of said counter is equal to the number of times which is continuously performing for one cycle when the deinterleaving sync is shifted according to said sync adjustment control signal in said deinterleaver.